Maximal Fat Oxidation is Related to Performance in an Ironman Triathlon

The aim of the present study was to investigate the relationship between maximal fat oxidation rate (MFO) measured during a progressive exercise test on a cycle ergometer and ultra-endurance performance. 61 male ironman athletes (age: 35±1 yrs. 23-47 yrs., with a BMI of 23.6±0.3 kg/m2 20.0-30.1 kg/m2, a body fat percentage of 16.7±0.7% 8.4-30.7% and a VO2peak of 58.7±0.7 ml/min/kg 43.9-72.5 ml/min/kg SEM Range) were tested in the laboratory between 25 and 4 days prior to the ultra-endurance event, 2016 Ironman Copenhagen. Simple bivariate analyses revealed significant negative correlations between race time and MFO (r2=0.12, p2peak (r2=0.45, p2=0.27, p2peak were not correlated. When the significant variables from the bivariate regression analyses were entered into the multiple regression models, VO2peak and MFO together explained 50% of the variation observed in race time among the 61 Ironman athletes (adj R2=0.50, p9 h). Furthermore, we demonstrate that 50% of the variation in Ironman triathlon race time can be explained by peak oxygen uptake and maximal fat oxidation.